Nestled in the middle of quaint in-town neighborhood of Philadelphia is what appears to be a massive fort which personally was very reminiscent of El Morro in Puerto Rico but with the greatest exception in that behind these walls, some of the US notorious criminals such as bank robber Willie Sutton and Al Capone where held inside at one point.

When the building was erected it was the largest and most expensive public structure ever constructed. The prison is currently a U.S. National Historic Landmark, which is open to the public as a museum for tours seven days a week.

Over the weekend, I reach out to local friends and upon informing them about this enormous and creepy edifice, we took the 2hr ride down to Philadelphia to explore the museum. I associated photographing inside almost to cheating because regardless of where you aim your camera, you’re likely to capture a very intriguing part of history no matter what.

The most wonderful part of the experience was the availability of self-guided tour so there’s absolutely no need to feel rushed. In fact, if you’re plan is to capture as much of this hidden treasure as possible, I recommend you venture along with someone who’s as fascinated with the idea of exploring a former prison and not someone who’s going to rush you to move along and put you at risk of missing interesting nooks and crannies inside.

To view the rest of the photographs of our excursion, head over to the Flickr set.